Partial-Beam Non-Orthogonal Multiple Access (PB-NOMA) With Fuzzy Clustering

Abstract

This letter proposes a partial-beam non-orthogonal multiple access (PB-NOMA) system for millimeter wave (mmWave) channels. In the proposed system, the user terminals (UT)s partially belong to different user groups and power-domain partial NOMA (P-NOMA) technique is exploited in their allocated spectrum. While an individual beam serves the UTs in one group, the UTs in the same group, including the overlapped beam UTs, employ the P-NOMA scheme. Overlapped beam UTs are present when two near UTs are closely correlated and when they are equally belonging to two user groups. Fuzzy C-means (FCM) clustering method, which considers the channel correlation coefficient as a similarity measure, is proposed to group the users. Then, user pairing is performed based on the channel gain differences and fuzzy membership values. Simulation results reveal that the sum-rate performance of the proposed PB-NOMA scheme with fuzzy clustering is shown to be better than that of the conventional P-NOMA systems by adjusting overlapped beam ratio (OBR) and lower near UT overlap ratio (NOR) in a preferable group.